1. Field of the Invention
The present invention relates to a transmission line and a device that includes the transmission line, and more particularly, a transmission line that is connected to a semiconductor device and a device including the transmission line.
2. Description of the Related Art
FIG. 1A shows a plan view of an interface at which pads 11 of an electric component 10 such as a semiconductor device are connected to a transmission line 20 by metal wires 31 such as gold wires (or gold ribbons). The transmission line 20 is of a coplanar type.
FIG. 1B is a cross-sectional view taken along a line A–A′ shown in FIG. 1A, and FIG. 1C is an equivalent circuit of the circuit configuration shown in FIG. 1A. The use of the metal wires 31 results in an electric capacitance between the metal wires and a metal frame 30 on which the component 10 and the transmission line 20 are formed. Symbols L1 and L2 are inductances of the metal wires 31, and Ld is an inductance of the transmission line 20.
In general, the capacitance C1 is much smaller than an electric capacitance Cd (C1<<Cd) on the side of the transmission line 20. This causes discontinuity of impedance between the component 10 and the transmission line 20. This kind of problem occurs in not only the coplanar type transmission line but also a transmission line of microstrip type.